JPS6337941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for observing a scanned image of a sample moving at a constant speed using a charged particle beam device.

A scanning electron microscope displays the sample area scanned by an electron beam as a scanned image on a cathode ray tube (CRT) screen. Observation of large samples requires moving the sample relative to the electron beam, which is difficult due to increased strain and other factors. A normal scanned image cannot be displayed while the sample is being moved, so in order to find the desired field of view within the surface of a large sample, the sample must be stopped each time the sample is moved a certain amount, and the scanned image on the CRT screen must be scanned. This operation was very troublesome as it required repeating the operation of confirming the .

The present invention aims to solve these drawbacks and display a clear scanned image even while the sample is moving. Therefore, the present invention provides horizontal and vertical deflection means for repeatedly scanning and deflecting a predetermined area within a reference plane on which an observation sample is placed by a charged particle beam, and horizontal and vertical scanning signals supplied to the deflection means. A scanning image display means to which synchronized scanning signals are supplied, and a constant speed such that the moving distance of the sample during the period T becomes an arbitrary value M, where T is the period of screen scanning in the scanning image display means. a constant velocity moving means for moving the sample in the horizontal scanning direction of the charged particle beam, and a starting position of the horizontal scanning of the charged particle beam within the reference plane is moved in the horizontal scanning direction by the distance M during scanning of one screen. The present invention is characterized in that means is provided for adding a sawtooth wave signal having a peak value proportional to the speed M/T and synchronized with the vertical scanning signal to the horizontal scanning signal supplied to the horizontal deflection means so as to .

FIG. 1 is a schematic diagram showing a device according to an embodiment of the present invention, in which reference numeral 1 indicates a sawtooth horizontal scanning signal shown in FIG. 2b and a period T (sec) several hundred times longer than the horizontal scanning signal.
FIG. 2a shows a scanning power supply for generating the vertical scanning signal shown in FIG. 2a. Part of the horizontal and vertical scanning signals from the scanning power supply 1 is supplied to the horizontal deflection coil 2X and vertical deflection coil 2Y of the cathode ray tube (CRT) 2, and the CRT screen with the horizontal width W (mm) and vertical width V (mm) is rasterized. scanned. The output scanning signal of the scanning power supply 1 (the horizontal scanning signal is passed through the adder circuit 3) is sent to the deflection coil 4.
x, 4y, and the deflection coil 4
The electron beam irradiating the sample 5 along the optical axis Z is deflected by x and 4y, and a predetermined area on the reference plane on which the sample surface is arranged is raster-scanned. The sample moving device 6 on which the sample 5 is placed is equipped with a mechanism that moves the sample 5 in the horizontal H and vertical V directions within a reference plane perpendicular to the optical axis Z, and the mechanism moves the sample 5 at a constant speed independently of manual operation. Pulse motors 7H and 7V are attached to perform this. Here, the deflection coil 4 is arranged so that the directions H and V of the sample movement coincide with the horizontal and vertical scanning directions x and y of the electron beam scanning on the reference plane, respectively.
It is assumed that the positional relationship between x, 4y and the sample moving device has been adjusted in advance. Each pulse motor 7H, 7
Of the drive power supplies 8H and 8V of V, 8H is controlled by the output of the movement control circuit 9.
The output is also supplied to the correction signal generation circuit 10.
The correction signal generating circuit 10 responds to an input speed signal, for example, a speed signal of M (mm) per cycle T (sec) of CRT screen scanning, so that the peak value of the signal changes to the speed signal M/ as shown in FIG. 2c. A sawtooth wave signal with a period T proportional to T is generated and the signal is supplied to the adder circuit 3. As a result, a scanning signal having a waveform as shown in FIG. 2d is supplied to the deflection coil 4x for the electron beam.

FIG. 3 shows the relationship between the sample 5 and the electron beam scanning area within the reference plane where the sample surface is installed. The area surrounded by the broken line S1 has a horizontal width w (mm) and a vertical width v ( mm), Fig. 2a,
The scanning area when deflection is performed based on the scanning signal shown in b is shown. In this state, the sample is in a stationary state, and the output of the correction signal generation circuit 10 is zero.
From this state, when the movement control circuit 9 is instructed to move the sample 5 to the left on the paper at a speed of M/T (M=w), the sample 5 moves in the direction of arrow 11 in FIG. 3, for example. Start moving at constant speed. Furthermore, since the scanning signal shown in FIG. 2d is supplied to the electron beam deflection coil 4x instead of that shown in FIG. 2a, the electron beam scanning area in the reference plane becomes the area SO surrounded by the solid line in FIG. , the regions S1, S2, . . . S6 in the sample 5 are switched and displayed every time the CRT screen is scanned. In this way, the scanned image displayed on the CRT screen is not only as clear and unshaken as if the sample were stationary, but also by sequentially switching the field of view for horizontal strips within the sample plane. This is an extremely convenient display method for observing the outline of a large sample.

By the way, when the sample movement speed M/T is increased and the movement control circuit 9 is operated as M=w+d, the output of the correction signal generation circuit 10 has a large peak value as shown in FIG. The waveform of the horizontal scanning signal supplied to the coil 4x is as shown in FIG. 2f. At this time, the scanning area of the electron beam on the reference plane is shown as SO' in Figure 4, and the observation areas in the sample plane cannot be observed in each area such as S1', S2', S3',...S6'. A region of width d results. Conversely, if the sample movement speed M/T is reduced and the movement control circuit 9 is operated so that M=w-d, the electron beam operation area on the reference plane becomes SO'' in Fig. 5, and the electron beam on the sample surface becomes The line operation areas become S1'', S2'', S3'',...S6'', and overlapping areas occur in the field of view of the scanned images that are sequentially switched and displayed on the CRT screen.

Note that the present invention is not limited to the embodiment device described above, and for example, the deflection coils 4x, 4
The adjustment between the y and the sample moving device may be incomplete, or
If the position of the reference plane changes in the optical axis Z direction,
Since the electron beam scanning directions x, y on the reference plane do not match the sample moving directions H, V, the rotation circuit 12 which adds a rotation signal to the scanning signals supplied to the deflection coils 4x, 4y is connected to the broken line in FIG. The relationship between the scanning directions x and y and the moving directions H and V may be adjusted by inserting them into the locations shown in FIG. Moreover, the rotation circuit 12
Instead, a rotation circuit 13 is inserted at the location indicated by the broken line 13 in FIG. By driving each at a constant rate, the directions H and V of sample movement can be arbitrarily rotated. By adjusting the rotation circuit 13, the scanning directions , V can be matched.

As explained above, in the present invention, a stationary scanned image of a sample moving at a constant speed is observed using a device that displays a scanned image by scanning the sample with a charged particle beam, such as a scanning electron microscope or an ion scanning microscope. This makes it possible to obtain effects such as easier field-of-field searching operations for large samples.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an apparatus according to an embodiment of the present invention, and FIGS. 2 to 5 are schematic diagrams for explaining the operation of the apparatus shown in FIG. 1: Scanning electron source, 2: CRT, 3: Adder circuit,
5: sample, 6: sample moving device, 7H, 7V: pulse motor, 8H, 8V: drive power supply, 9: movement control circuit, 10: correction signal generation circuit, 12, 13: rotation circuit.

Claims (1)

[Claims] 1. Horizontal and vertical deflection means for repeatedly scanning and deflecting a predetermined area within a reference plane on which an observation sample is placed by a charged particle beam, and a scanning signal synchronized with the horizontal and vertical scanning signals supplied to the deflection means. charge the sample at a constant speed such that the moving distance of the sample during the period T becomes an arbitrary value M, where T is the period of screen scanning in the scanning image display means and a constant velocity moving means for moving the particle beam in the horizontal scanning direction; and a constant velocity moving means for moving the charged particle beam in the horizontal scanning direction; A moving sample observation device comprising: means for adding a sawtooth wave signal having a peak value proportional to the speed M/T and synchronized with the vertical scanning signal to the horizontal scanning signal supplied to the horizontal deflection means. .